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Ben Livneh, Ph.D.Visiting Postdoctoral FellowCooperative Institute for Research in Environmental Sciences (CIRES)Western Water Assessment
Wednesday, January 16, 2013 - 3:00pmFL2, Room 1001
The Colorado River Basin is an essential freshwater resource for the southern Rocky Mountains and southwestern U.S. The majority of water originates in the headwaters region and hence changes to this region will largely control downstream water availability. Understanding the role of climatic change and land cover disturbances on hydrology is of growing importance for water managers in light of steady increases in demand. Numerous studies have identified appreciable inter-annual variability in historical precipitation, which in combination with warming temperatures could have severe implications on future water supply. More recently, the northern headwaters region has suffered widespread tree kills due to Mountain Pine Beetle (MPB) infestation across a range of forest types, elevation, and latitude. Additionally, the incidence and severity of desert dust-on-snow events have risen in the past decade, causing increased radiative transfer and snowmelt rates within headwaters snowpacks, shifting peak snowmelt runoff earlier in the year. In this presentation, I will first explore hydrologic impacts of the latter two disturbance factors in a hydrologic modeling framework. Next, I will discuss issues associated with separating these impacts from climatic factors and present some relevant results. The Distributed Hydrology Soil Vegetation Model (DHSVM) was selected to simulate hydrologic conditions over a set of 4 candidate catchments within the headwaters region that offer a gradient in MPB impacts, dust-on-snow severity, elevation, and forest coverage. The observational data sets include meteorological forcings of precipitation, maximum and minimum temperature, time series maps of leaf area index (LAI), as well as other forest cover properties derived from MODIS forest phenology and aerial survey data. Experiments are focused on examining the impacts of changing LAI and phenology cycles (from MPB), and snow surface albedo properties (from dust-on-snow events) on streamflow and hydrologic fluxes, such as snow water equivalent. It is expected that these results will lead to a clearer understanding of current and future drivers for change in hydrologic response and identify key issues going forward.